Heat exchanger



April 26, 1955 A. KooPMANs HEAT EXCHANGER Filed Jan. 4, 1951 INVENTOR ADRIAAN KooPMANs BY y United States Patent O HEAT EXCHAN GER Adriaan Koopmans, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application January 4, 1951, Serial No. 204,315 Claims priority, application Netherlands January 26, 1950 3 Claims. (Cl. 257-241) This invention relates generally to heat exchangers. More particularly, the invention relates to those heat exchangers comprising channels for two media which are in heat-transfer relation; one of said media being a liquid and the other a gas.

It is known in the prior art to build up heat exchangers from plate-shaped elements, which are spaced apart by a definite distance. In such arrangements, the media flow through the channels thus formed and the heat transfer takes place through the plate-shaped elements which thus function as partitions. Constructions are furthermore known, in which the channels for one medium consist of pipes, over which the other medium passes.

The above two prior constructions have a limitation in that they are unsuitable for mass-production when these heat exchangers are to be used in hot-gas reciproeating engines, for example. Therein an overall circular configuration is necessary so that it is not easily possible to fulfill the particular conditions imposed on heat exchangers for this use. Moreover, the elements of the aforesaid known heat exchangers are generally secured together by soldering, which often involves great difliculties. The disadvantages of these known heat exchangers are avoided in the heat exchanger according to the present invention.

To this end, the heat exchanger according to the 1nvention has the feature that the channels for the liquid are comprised of a number of tubes which are surrounded by metal cast therearound. The said cast metal then also contains the channels for the gas. This construction 1s extremely suitable for mass-production and, furthermore, permits the boundary of the channels for the gas to consist either of thin walls of sheet material or of the cast material itself.

The heat exchanger according to the invention has, furthermore, the advantage set out hereinafter. Cast metal has, in general, the characteristic of being sl1ghtly porous. If channels for the two media to be 1n heattransfer relation are bored in a block of cast metal, leakage may occur through the metal if the pressure of one medium, for example, a gas, materially exceeds that of the other medium. This leakage may be avoided by making the partitions between the channels very thick, but in such event the heat-transfer between the two media is then very unsatisfactory. By the construction according to the present invention, this disadvantage is obviated since one medium, i. e. the liquid, ows through a plurality of tubes embedded in the cast metal. Tube material, in general, has the feature of being substantially non-porous. The construction according to the invention thus has the advantage that, since gas leakage is avoided, the partitions between the channels for the two media can be thin. Furthermore, the heat transfer through these metals is satisfactory. The gas leakage to the outside of the heat-exchanger may be avoided by making the wall sufficiently thick, which is not objectionable in this heat-exchanger, since no heat transfer need occur through this wall.

According to the invention, it has furthermore been found to be particularly advantageous to provide that the channels for the liquid have a circular or substantially circular sectional area and that the channels for the gas be shaped in the form of slits. In the present case, the term substantially circular sectional area is to be understood also to include such sections, for example, as oval sections, and rectangular sections having round corners. The channels for the liquid will generally have to be cleaned after a certain period of time, which operation is facilitated by the provision of a circular or substantially circular sectional area. From a thermal point of view it is advantageous to use slit-shaped channels for the gas, to ensure a proportionately large heat transferring surface relative to the stream of gas flowing therethrough. Such slit-shaped channels for the gas are feasiblledsince these channels do not become substantially soi e i In accordance with a further feature of the invention, the heat exchanger is formed in the shape of a hollow cylinder with the slit-shaped channels extending according to a generatrix of the cylinder and opening out at the cylindrical surface. Each channel for one medium is preferably located between two channels for the other medium.

In addition, the channels for each medium are preferably arranged parallel to one another.

For a simple manufacture of the heat-exchanger, it will often be advisable that the inlet and outlet ports of the channel system for the liquid should be located at the cylindrical surface thereof. In certain cases it is desirable for the construction of the heat-exchanger to provide it with a wall through which the tubes for the liquid pass, which tubes are secured to the wall. In this manner, the position of the tubes is fixed on casting the metal around them and any gas leaks to the outside of the heat-exchanger can thus be prevented by the said wall which may function as an outer impervious shell.

According to another feature of the invention, it is desirable, for a satisfactory adherence of the aforesaid tubes to the metal cast around them, that an intimate contact should be established between the two metals to ensure a satisfactory heat transfer. Therefore, the tubes for the liquid are preferably made of copper and embedded in an aluminium alloy.

The heat-exchanger according to the invention can be made in a simple manner by forming the slit-shaped channels by providing core plates prior to the casting operation and subsequently removing these plates.

The heat-exchangers described above may be used with particular advantage as coolers for a hot-gas reciprocating engine. In this case, the term a hot-gas reciprocating engine is to be understood to include as well a cold-gas cooling machine operating according to the reversed hotgas engine principle. The conditions imposed on a cooler for a hot-gas reciprocating engine are satisfied by the cooler according to the invention. With such coolers, for example, the different conditions set forth hereinbefore imposed on the channels for the liquid on the one hand, and on the channels transversed by the gas on the other, are niet. That is to say, in hot-gas reciprocating engines, the gaseous working medium flows through the last-mentioned channels to obtain the advantages described. In addition, in connection with the clearance space of the engine, it is desirable that not only the length of flow but also the sectional area of these gas channels should be as small as possible. This, too, is achieved with the present invention.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described in detail with reference to the accompanying drawing, which represents one embodiment of the heatexchanger according to the invention.

Fig. l is a vertical sectional view taken on the line I-I in Fig. 2; and

Fig. 2 is a horizontal sectional view on the line ll--ll in Fig. l.

The heat exchanger according to the invention comprises a housing 1 enclosing tubes 2. These tubes, which are preferably made of copper, are embedded in a different metal 3, preferably an aluminium alloy, cast around them. Owing to the difference of shrinkage between the aluminium alloy and copper, an intimate Contact is established between the two metals. In the metal 3 provision is made of slit-shaped channels 4 which are formed by providing core plates prior to, and removing them after, the casting operation. The slit-shaped channels are bounded by a bushing or barrier sheath 5 provided at the inner periphery of the annular heat-exchanger.. An annular supply channel 6 is secured to the housing 1 through which the cooling liquid is supplied to the parallel tubes 2. An annular exhaust channel 9 is connected to the housing through which the cooling uid is exhausted from the pipes 2 as at 8. This cooling liquid enters the channel at A and leaves it at B. The gaseous medium traverses the heat-exchanger in a vertical sense, as is indicated by the arrow C.

The wall portion 3a may be thin, since gas leaks are avoided by the ring 1. Even in the absence of the ring 1, gas leaks due to porosity of the metal are avoided by a greater wall thickness of the portion 3a. This is not disadvantageous, since this wall portion does not partake in any heat exchange. In this present heat exchanger, the cast metal portion between each slit 4 and each tube 2, through which the heat exchange does take place, may be thin since the tubes prevent the gas from leaking into the liquid channels defined therein.

Preferably the tubes 2 are secured to the housing 1 at 7 and 8 prior to the casting operation. This allows keeping the tubes 2 accurately spaced apart, so that an exact construction is ensured.

While the invention has been described with reference to the illustrated embodiment, it is to be understood that it is not limited thereto, but that changes and modifications may be made therein within the scope of the appended claims.

What I claim is:

1. A heat exchange device for two media, one of which is liquid and the other a gas, comprising; at least two spaced tubes for conduction of said liquid, a cast metal body of substantially annular shape having said tubes embedded therein, an annular inner barrier sheath secured to the inner periphery of said cast metal body, and a slitshaped channel for conduction of said gas positioned between said spaced tubes and extending substantially parallel to the longitudinal axis of said cast metal body, said channel opening out at the inner periphery of said cast metal body.

2. A heat exchange device for two media, one of which is liquid and the other a gas, comprising; at least two spaced tubes for conduction of said liquid, a cast metal body of substantially annular shape having said tubes embedded therein, an annular inner barrier sheath secured to the inner periphery of said cast metal body,.a slit-shaped channel for conduction of said gas positioned between said spaced tubes and extending substantially parallel to the longitudinal axis of said cast metal body and completely therethrough, said channel opening out at the inner periphery of said cast metal body, and inlet and outlet ports for each of said tubes, each of said inlet and outlet ports being located at the outer periphery of said body.

3. A heat exchange device for two media, one of which is a liquid and the other a gas, comprising: a plurality of tubes arranged in pairs and adapted to conduct the liquid, said tubes being embedded in a substantially annular shaped cast metal body, slit-shaped channels extending radially in said body, each of said channels being located between adjacent pairs of said tubes and adapted to conduct the gas, said channels opening out in the inner periphery of said body and extending completely through said cast metal body in a direction parallel to the longitudinal axis of said cast metal body, a separate inner liner abutting said inner periphery to close off said channel openings, an outer wall surrounding the outer periphery of said body, said tubes having the ends thereof passing through said outer wall.

References Cited in the le of this patent UNITED STATES PATENTS 2,443,295 Bisch June 15, 1948 2,460,889 Larsen Feb. 8, 1949 2,464,900 Stigter Mar. 22, 1949 2,466,676 Boling et al. Apr. 12, 1949 2,476,151 Le Jeune July 12, 1949 2,499,448 Axelson et al. Mar. 7, 1950 2,507,177 Vermeer May 9, 1950 FOREIGN PATENTS 345,794 Great Britain Apr. 2, 1931 

3. A HEAT EXCHANGE DEVICE FOR TWO MEDIA, ONE OF WHICH IS A LIQUID AND THE OTHER A GAS, COMPRISING: A PLURALITY OF TUBES ARRANGED IN PAIRS AND ADAPTED TO CONDUCT THE LIQUID, SAID TUBES BEING EMBEDDED IN A SUBSTANTIALLY ANNULAR SHAPED CAST METAL BODY, SLIT-SHAPED CHANNELS EXTENDING RADIALLY IN SAID BODY, EACH OF SAID CHANNELS BEING LOCATED BETWEEN ADJACENT PAIRS OF SAID TUBES AND ADAPTED TO CONDUCT THE GAS, SAID CHANNELS OPENING OUT IN THE INNER PERIPHERY OF SAID BODY AND EXTENDING COMPLETELY THROUGH SAID CAST METAL BODY IN A DIRECTION PARALLEL TO THE LONGITUDINAL AXIS OF SAID CAST METAL BODY, A SEPARATE INNER LINER ABUTTING SAID INNER PERIPHERY TO CLOSE OFF SAID CHANNEL OPENINGS, AN OUTER WALL SURROUNDING THE OUTER PERIPHERY OF SAID BODY, SAID TUBES HAVING THE ENDS THEREOF PASSING THROUGH SAID OUTER WALL. 